hey guys i just wanted to know what people think the best motocross dirt bike is for a 13 year old 4'11 tall 110 llb boy is, and why. and also would it be good to ride on trails or just to race with?

I have been riding since i was 5 years old, i want to kno what type of bike would be great for motocross and what type of work i should do to make it faster.